Panoramic imaging device

ABSTRACT

A panoramic imaging device comprises: a photodetector array; a lens array having, on one plane, a center lens for receiving light in a front range of 36° to form a central unit image on the photodetector array, and left and right side lenses for receiving lights in left and right ranges each of 72° in capture angle of 180°; and four prisms in two pairs placed facing the side lenses. The two pairs of left and right prisms (more inclined and less inclined pairs) collect lights in divided two pairs of left and right ranges each of 36° in the 72° range (pairs closer to, and farther from, the front range), respectively, to form four side unit images on the photodetector array which are combined with the central unit image to reproduce a panoramic image without using wide-angle lenses or complex image correction process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application contains related subject matter to the Assignee'sco-pending application Ser. Nos. 11/846,806, filed Aug. 29, 2007, and11/736,267, filed Apr. 17, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a panoramic imaging device.

2. Description of the Related Art

Various devices for capturing images positioned therearound in a widecapture angle or range are known, such as a monitor camera and amonitoring system for monitoring obstacles around a car. For example, aknown camera device for monitoring three directions around a car, thatare front, left and right, uses prisms placed on the light entrance sideof an imaging element, such that the prisms refract or bend lightsentering in the left and right directions or ranges so as to form imagesin predetermined areas on the imaging element, while forming an image ina separate area on the imaging element based on light entering in thefront direction or range without passing through the prisms. The formedleft and right images and the formed front image are separatelydisplayed on a monitor screen (refer, for example, to Japanese Laid-openPatent Publication 2003-207836). A known wide-angle imaging device usesmultiple optical imaging units for forming optical images on an imageplane or focal plane, such that the optical axes of the multiple opticalimaging units intersect at one point near a lens, and that the imageviewing angles or ranges of adjacent ones of the optical imaging unitsare contiguous. The images captured by the respective optical imagingunits are reproduced as a panoramic image, which is displayed on amonitor screen (refer, for example, to Japanese Laid-open PatentPublication 2006-25340).

In the known imaging devices, there are problems to be solved. Thecamera device described in the first cited patent publication (JapaneseLaid-open Patent Publication 2003-207836) makes it possible to obtainimages in the three directions, front and left/right of the car.However, these images are displayed on the monitor screen as threeindependent images without being reproduced as a continuous image(panoramic image). Further, in order to allow the camera device tomonitor a wide range such as about 180° (degrees) around the cameradevice, each of the three images in the three directions is required tohave a picture angle of 60° (degrees) or larger. This requires the useof so-called wide-angle lenses as imaging lenses. However, a wide-anglelens is likely to cause barrel distortion at periphery of an imagecaptured thereby. Although it is possible to digitally correct thebarrel distortion at the peripheries of images, a complex program isnecessary to correct the barrel distortion.

The wide-angle imaging device described in the second cited patentpublication (Japanese Laid-open Patent Publication 2006-25340) makes itpossible to reproduce a panoramic image from the images captured by therespective optical imaging units. When the wide-angle imaging device isused as a monitor camera, a high monitoring function can be obtainedwithout causing so-called dead angles (non-imaging area) between theimages. However, this wide-angle imaging device has a problem in thatthis imaging device is likely to become large in volume in its entiretybecause the multiple optical imaging units are placedthree-dimensionally.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a panoramic imagingdevice for imaging a panoramic image with a picture angle of at leastapproximately 180°, which can be formed without using a wide-angle lenshaving a capture angle larger than 60°, and which can combine multipleimages into a panoramic image without complex image correction andwithout causing unnatural transition between adjacent images to remain,and further which can be reduced in volume and thickness in itsentirety.

According to a first aspect of the present invention, this object isachieved by a panoramic imaging device comprising: an optical lenssystem for collecting light entering in a capture angle of at least 180°so as to form images on a predetermined focal plane; imaging meansplaced at the focal plane for converting the images formed by theoptical lens system to electronic image information; and imagereproducing means for subjecting the electronic image informationobtained from the imaging means to imaging processing so as to reproducea panoramic image.

The optical lens system comprises: an optical lens array including acenter lens having an optical axis and formed on one plane for receivinglight entering in a front range in the capture angle, and also includingpairs of left and right side lenses formed on the one plane and on leftand right sides of the center lens, respectively, and which have opticalaxes parallel to that of the center lens, so as to respectively receivelights entering in left and right ranges in the capture angle, which aredivided into pairs of left and right ranges such that the pairs of leftand right side lenses receive lights entering in the divided pairs ofthe left and right ranges, respectively; and prisms placed on a lightentrance side of the side lenses for bending and collecting the lightsentering in the divided pairs of the left and right ranges in thecapture angle for the side lenses to receive, so as to guide and directthe lights to, and along the optical axes of, the side lenses,respectively.

The imaging means is formed of a photodetector array placed at apredetermined distance from, and in parallel to, the optical lens arrayfor capturing an image formed by the center lens and images formed bythe left and right side lenses. Further, the image reproducing meanscombines the image formed by the center lens in the front range in thecapture angle with the images respectively formed by the pairs of leftand right side lenses in the divided pairs of left and right ranges inthe capture angle so as to reproduce a panoramic image with a pictureangle of at least 180°.

Preferably, each of the lights received by the center lens and the sidelenses is light entering in a range smaller than approximately 60° inthe capture angle of at least 180°.

Further preferably, the capture angle is approximately 180°, wherein thelight received by the center lens is light entering in a front range ofapproximately 36° in the capture angle, and wherein the side lenses arecomposed of two left side lenses and two right side lenses which receivelights entering in divided two pairs of left and right ranges each ofapproximately 36°, respectively, which enter in a pair of left and rightranges each of approximately 72° in the capture angle, respectively.

Still further preferably, the capture angle is approximately 180°,wherein the light received by the center lens is light entering in afront range of approximately 26° in the capture angle, and wherein theside lenses are composed of three left side lenses and three right sidelenses which receive lights entering in divided three pairs of left andright ranges each of approximately 26°, respectively, which enter in apair of left and right ranges each of approximately 77° in the captureangle, respectively.

According to a second aspect of the present invention, theabove-described object is achieved by a panoramic imaging devicecomprising: an optical lens system for collecting light entering in acapture angle of approximately 180° so as to form images on apredetermined focal plane; imaging means placed at the focal plane forconverting the images formed by the optical lens system to electronicimage information; and image reproducing means for subjecting theelectronic image information obtained from the imaging means to imagingprocessing so as to reproduce a panoramic image.

The optical lens system comprises: an optical lens array including acenter lens having an optical axis and formed on one plane for receivinglight entering in a front range of approximately 36° in the captureangle, and also including two pairs of left and right side lenses formedon the one plane and on left and right sides of the center lens,respectively, and which have optical axes parallel to that of the centerlens, so as to respectively receive lights entering in left and rightranges each of approximately 72° in the capture angle, which are dividedinto two pairs of left and right ranges each of approximately 36° suchthat the two pairs of left and right side lenses receive lights enteringin the divided two pairs of the left and right ranges, respectively; andtwo pairs of left and right right-angle prisms placed on a lightentrance side of the side lenses, and respectively facing the sidelenses at positions to prevent interruption of the light entering thecenter lens in the front range of approximately 36°, for bending andcollecting the lights entering in the divided two pairs of the left andright ranges each of approximately 36° in the capture angle for the sidelenses to receive, so as to guide and direct the lights to, and alongthe optical axes of, the side lenses, respectively.

The imaging means is formed of a photodetector array placed at apredetermined distance from, and in parallel to, the optical lens arrayfor capturing an image formed by the center lens and images formed bythe two pairs of left and right side lenses. Further, the imagereproducing means combines the image formed by the center lens in thefront range of approximately 36° in the capture angle with four imagesrespectively formed by the two pairs of left and right side lenses inthe divided two pairs of left and right ranges each of approximately 36°in the capture angle so as to reproduce a panoramic image with a pictureangle of approximately 180°.

The panoramic imaging device according to the present invention can beformed without using optical lenses having a large capture angle(wide-angle lenses) such as 60° or larger, making it possible for theformed images to have substantially no distortions, so that no complexprocess of image correction for the images is required when combiningthe images, and that images can be combined into a panoramic image of apicture angle of at least or approximately 180° without causingunnatural transition between adjacent images. This also makes itpossible to reduce the volume and thickness of the entire panoramicimaging device.

While the novel features of the present invention are set forth in theappended claims, the present invention will be better understood fromthe following detailed description taken in conjunction with thedrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described hereinafter with reference tothe annexed drawings. It is to be noted that all the drawings are shownfor the purpose of illustrating the technical concept of the presentinvention or embodiments thereof, wherein:

FIG. 1 is a schematic perspective view of a panoramic imaging deviceaccording to an embodiment of the present invention;

FIG. 2 is a schematic front view of an optical lens system in thepanoramic imaging device;

FIG. 3 is a schematic expanded cross-sectional view along line A-A inFIG. 2, showing an optical path diagram of the optical lens system ofthe panoramic imaging device with a light flux passing through eachlens;

FIG. 4A and FIG. 4B are schematic perspective views of the panoramicimaging device placed facing a target object to be imaged in a range of180° as seen from diagonally left above and diagonally right above,respectively;

FIG. 5 is a schematic view of, on the left, a matrix image of unitimages on a photodetector array of the panoramic imaging device as wellas matrix images in the middle and on the right, showing a process ofhow the unit images, as image information, are processed to form apanoramic image;

FIG. 6 is a schematic front view of a panoramic imaging device accordingto a first modified example; and

FIG. 7 is a schematic front view of a panoramic imaging device accordingto a second modified example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention, as best mode for carrying out theinvention, will be described hereinafter with reference to the drawings.The present invention relates to a panoramic imaging device. It is to beunderstood that the embodiments described herein are not intended aslimiting, or encompassing the entire scope of, the present invention.Note that like parts are designated by like reference numerals,characters or symbols throughout the drawings.

Referring to FIG. 1 to FIG. 5, a panoramic imaging device 1 according toan embodiment of the present invention will be described. As shown inFIG. 1 to FIG. 3, the panoramic imaging device 1 of the presentembodiment comprises: an optical lens system 2 for collecting lightentering therein in a capture angle (picture-taking angle) of at least180° (approximately 180°) so as to form images on a predetermined focalplane; a photodetector array (claimed “imaging means”) 3 placed at thefocal plane of the optical lens system 2 for converting the imagesformed by the optical lens system 2 to electronic image information; anda processing circuit for signal processing and display. The processingcircuit comprises: an A/D (Analog-to-Digital) converter 4 for convertingthe electronic image information from the photodetector array 3 to adigital signal; a DSP (Digital Signal Processor) 5 for receiving thedigital signal of the electronic image information converted from theimages by the photodetector array 3; and an image reproductionmicroprocessor (claimed “image reproducing means”) 6 for subjecting thedigital signal of the image information received by the DSP 5 to imageprocessing to reproduce a panoramic image; and a display unit 7 such asa liquid crystal panel for displaying the panoramic image reproduced bythe image reproduction microprocessor 6.

The optical lens system 2 according to the present embodiment comprises:an optical lens array 9 having 9 (nine) optical lenses L which havemutually parallel optical axes La, and which are arranged in a matrix of3 (three) rows and 3 (three) columns and integrally formed as singleconvex lenses on one plane or surface of a transparent substrate 8; andfour 45-45-90 degree right-angle prisms P, two on the left and two onthe right, placed on the light entrance side of the optical lens array 9to face four optical lenses L, respectively. Hereafter, the respectiveoptical lenses L are designated by, and distinguished from each otherby, suffixes appended thereto and corresponding to the positions thereofin the matrix of 3 rows and 3 columns. For example, the optical lens Lin row 1 (first row)-column 1 (first column) is designated by L1-1.

The four 45-45-90 degree right-angle prisms P are placed facing theoptical lenses L1-1, L1-3, L3-1, L3-3, respectively. Hereafter, therespective 45-45-90 degree right-angle prisms P are also designated by,and distinguished from each other, by suffixes appended thereto andcorresponding to the positions thereof. For example, the 45-45-90 degreeright-angle prism P placed facing the optical lens L1-1 in row 1-column1 is designated by P1-1 (refer to FIG. 1 and FIG. 2). As shown in FIG.3, each of the 45-45-90 degree right-angle prisms P1-1, P1-3, P3-1, P3-3has a cross-section of a right-angle isosceles triangle with two sidesPa, Pb containing the right angle and a hypotenuse Pc facing the rightangle, and is inclined to the optical lens array 9.

The 45-45-90 degree right-angle prism P1-1 and the 45-45-90 degreeright-angle prism P1-3 are inclined at a relatively large angle(approximately 26°) to the optical lens array 9, while the 45-45-90degree right-angle prism P3-1 and the 45-45-90 degree right-angle prismP3-3 are inclined at a relatively small angle (approximately 10°) to theoptical lens array 9. Note that FIG. 3 shows an expanded cross-sectionalong line A-A in FIG. 2. All the nine optical lenses L1-1, L1-2, have acapture angle of 36°, which is smaller than 60° and is thus notrelatively large, so that images formed by the respective optical lensesare substantially free of distortion. Note here that although not shown,a stop member is placed between the optical lens array 9 and each of the45-45-90 degree right-angle prisms P1-1, P1-3, P3-1, P3-3. Further notethat the optical lenses L1-1, L1-2, . . . are not required to beintegrally formed on the transparent substrate 8, and e.g. can be heldby a lens holder so as to be arranged on a two-dimensional plane.

As shown in FIG. 3, the optical lens L2-2 at a central position(hereafter referred to as “center lens”) directly receives lightentering in a front range of approximately 36° in the capture angle,while the four optical lenses L1-1, L1-3, L3-1, L3-3 (hereafter referredto as “side lenses”) receive lights entering in left and right rangeseach of approximately 72° in the capture angle, more specifically in twodivided ranges each of approximately 36° in the left and right ranges,i.e. total four ranges each of approximately 36° through the 45-45-90degree right-angle prisms P1-1, P1-3, P3-1, P3-3, respectively. Each of45-45-90 right-angle prisms P1-1, P1-3, . . . is placed such that lightenters through an outward side Pa of the two sides Pa, Pb containing theright angle, and is reflected by the hypotenuse Pc and emitted throughthe other side Pb, so as to guide and direct the light (to enter eachoptical lens L) to, and along the optical axis of, the each optical lensL. In the present specification, surfaces of each right-angle prism Pfor guiding and allowing light to enter through and for reflecting andemitting the light are referred to as “sides” and “hypotenuse” in orderto describe such surfaces with reference to the optical path diagram ofFIG. 3.

More specifically, as shown in FIG. 3, the 45-45-90 right-angle prismsP1-1 and P1-3 are arranged to bend and collect lights entering in rangesZ1 (hereafter referred to as “first left and right ranges”) each ofapproximately 36° which are divided ranges in the left and right rangeseach of approximately 72°, and which are adjacent to (closer to), andleft and right of, the front range of approximately 36°, respectively,so as to guide the lights to the optical lenses L1-1, L1-3. On the otherhand, the 45-45-90 right-angle prisms P3-1 and P3-3 are arranged to bendand collect lights entering in ranges Z2 (hereafter referred to as“second left and right ranges”) each of approximately 36° which aredivided ranges in the left and right ranges each of approximately 72°,and which are adjacent to, and left and right of, the first left andright ranges Z1, respectively, (i.e. which are farther from the frontrange of approximately 36° than the first left and right ranges Z1) soas to guide the lights to the optical lenses L3-1, L3-3.

The light collected by each of the 45-45-90 degree right-angle prismsP1-1, P1-3, P3-1, P3-3 is reflected by the hypotenuse Pc of each of theprisms P1-1, P1-3, P3-1, P3-3 and emitted through the other side Pb ofeach such prism facing the optical lens array 9, so that the thusemitted lights from the 45-45-90 degree right-angle prisms P1-1, P1-3,P3-1, P3-3 are collected by the side lenses L1-1, L1-3, L3-1, L3-3,respectively. Note that no portion of the 45-45-90 degree right-angleprisms P exists in the front range of approximately 36° in the captureangle as seen from the center lens L2-2, so that the light entering thecenter lens L2-2 is not prevented from being interrupted.

Putting in another way, the left and right side lenses L1-1, L1-3 andthe left and right side lenses L3-1, L3-3 receive lights in left andright ranges each of 72° in the capture range of approximately 180°. Apair of left and right 45-45-90 degree right-angle prisms P1-1, P1-3(more inclined to the optical lens array 9 than the 45-45-90 degreeright-angle prisms P3-1, P3-3) bend and collect lights in a pair offirst left and right ranges Z1 each of approximately 36° in the 72°range, and guide the lights to the side lenses L1-1, L1-3. On the otherhand, a pair of left and right 45-45-90 degree right-angle prisms P3-1,P3-3 (less inclined to the optical lens array 9 than the 45-45-90 degreeright-angle prisms P1-1, P1-3) bend and collect lights in a pair ofsecond left and right ranges Z2 each of approximately 36° in the 72°range, and guide the lights to the side lenses L3-1, L3-3. Note herethat it is apparent that the capture angle of approximately 180° can beexpanded by simply increasing the capture range of each optical lens Land each prism P to bend, collect and guide light to each optical lensL.

Next, the photodetector array 3 will be described. The photodetectorarray 3 is placed at a predetermined distance from, and in parallel to,the optical lens array 9. More specifically, the photodetector array 3has major planes parallel to those of the optical lens array 9. Thephotodetector array 3 used herein is a solid-state imaging elementformed, for example, of a semiconductor substrate having imaging areason a focal plane of the respective optical lenses L1-1, L1-2, . . . ,and is, for example, a CMOS (Complementary Metal Oxide Semiconductor)image sensor. The solid-state imaging element (photodetector array 3)can also be a CCD (Charge Coupled Device).

Nine unit images F are formed on the photodetector array 3 by the nineoptical lenses L1-1, L1-2, in the matrix of 3 rows and 3 columns.Similarly as in the optical lenses L1-1, L1-2, . . . , the respectiveunit images F are designated by, and distinguished from each other by,suffixes appended thereto and corresponding to the positions thereof inthe matrix of 3 rows and 3 columns. For example, the unit imagecorresponding to the optical lens L1-1 is designated by F1-1. As willalso be described with reference to FIG. 5, the unit image F2-2 formedby the center lens L2-2 is inverted up/down and left/right from anoriginal image. On the other hand, the unit images F1-1, F1-3, F3-1,F3-3 formed by the side lenses L1-1, L1-3, L3-1, L3-3 are inverted onlyup/down from original images because the left/right inversion iseliminated by a mirror effect of each of the 45-45-90 degree right-angleprisms P1-1, P1-3, P3-1, P3-3.

Referring to FIG. 4A, FIG. 4B and FIG. 5, the operation of the panoramicimaging device 1 will be described in detail. FIG. 4A and FIG. 4B areschematic perspective views of the panoramic imaging device 1 placedfacing a target object B to be imaged in a range of 180° as seen fromdiagonally left above and diagonally right above, respectively. On theother hand, the image on the photodetector array 3 shown in the leftmatrix image of FIG. 5 is an image as seen from the target object B.Here it is assumed that as shown in FIG. 4A and FIG. 4B, the targetobject B placed in front of the panoramic imaging device 1 hasequiangular (or equilength) image segments of “Q”, “C”, “R” and “P” insuccessive 36° angular ranges in the capture angle (picture-takingangle) of 180°. In this case, the central image segment of “C” (i.e.center image segment in the center 36° angular range) is invertedup/down and left/right by the center lens L2-2 as described above toform the unit image F2-2 of “C” at the center of the photodetector array3, which, however, is inverted only up/down from the original imagesegment of “C” when such unit images F2-2 of “C” is seen from the targetobject B.

Note that in the present embodiment, not only the center lens L2-2 butalso the optical lenses L1-2, L2-1, L2-3, L3-2 receive lights enteringin the front range of approximately 36°. Accordingly, as shown in theleft matrix image of FIG. 5, the unit images F1-2, F2-1, F2-3, F3-2,which are inverted up/down from the original image segment of “C” at thecenter of the target object B, are formed at corresponding positions onthe photodetector array 3. On the other hand, the image segment of “L”and the image segment of “R” in the first left and right ranges Z1adjacent to the front range of 36° (designated by Z0 in FIG. 4A and FIG.4B) are inverted left/right by the 45-45-90 right-angle prisms P1-1,P1-3, respectively, and are then inverted up/down and left/right by theside lenses L1-1, L1-3, respectively, to form unit images F1-1, F1-3 of“R” and “L” at corresponding positions on the photodetector array 3 asshown in the left matrix image of FIG. 5. These unit images of “L” and“R” when seen from the target object B, are inverted up/down andleft/right as shown in the left matrix image of FIG. 5.

In a similar manner, the image segment of “Q” and the image segment of“P” in the second left and right ranges Z2 adjacent to the first leftand right ranges Z1 are inverted left/right by the 45-45-90 right-angleprisms P3-1, P3-3, respectively, and are then inverted up/down andleft/right by the side lenses L3-1, L3-3, respectively, to form unitimages F3-1, F3-3 of “P” and “Q” at corresponding positions on thephotodetector array 3 as shown in the left matrix image of FIG. 5. Theseunit images of “Q” and “P”, when seen from the target object B, areinverted up/down and left/right as shown in the left matrix image ofFIG. 5.

These nine unit images F1-1, F1-2, . . . are converted by thephotodetector array 3 to image information. The image informationgenerated by the conversion on the photodetector array 3 aresequentially read from the lowermost-leftmost pixel to theuppermost-rightmost pixel of the photodetector array 3 shown in the leftmatrix image of FIG. 5. As shown in the middle matrix image(intermediate step) of FIG. 5, the sequentially read image informationare inverted up/down from the image information on the photodetectorarray 3 shown in the left matrix image of FIG. 5 for restoration ofnormal images. However, the images of “P”, “Q”, “L” and “R” except for“C” are still not fully restored to be normal.

More specifically, the positions of the left and right columns of “P”,“Q”, “L” and “R” are exchanged with or reversed from the originalpositions of “P”, “Q”, “L” and “R” on the target object B, while theimages of “P”, “Q”, “L” and “R” per se in the left and right columns inthe middle matrix image in FIG. 5 are inverted left/right from theoriginal images of “P”, “Q”, “L” and “R” on the target object B. Theseimage information in the middle matrix image in FIG. 5 are processed bythe image reproduction microprocessor 6 to reverse the positions of theleft and right columns, and to invert the images of “P”, “Q”, “L” and“R” per se therein, thereby reproducing a panoramic image (one-rowmatrix image) PF with a picture angle of 180° (degrees) as shown in FIG.5. Note that the middle matrix image of FIG. 5 shows an image at anintermediate step in the process performed by the image reproductionmicroprocessor 6, and can be displayed on the display unit 7. This willbe described in more detail below.

The image reproduction microprocessor 6 performs image processing basedon the image information of the five unit images F3-1, F3-3, F2-2, F1-1,F1-3 of “P”, “Q”, “C”, “R” and “L” in the middle matrix image indicatedby bold frames f in FIG. 5. More specifically, the image reproductionmicroprocessor 6 mirror-inverts, and thereby restores, the unit imagesF3-1, F3-3, F1-3, F1-1 of “P”, “Q”, “L” and “R” (having been invertedleft/right) back to normal images of “P”, “Q”, “L” and “R”,respectively, and then combines these normal images of “P”, “Q”, “L” and“R” with the center unit image of “C” by properly positioning the normalimages of “P”, “Q”, “L” and “R” relative to the center unit image of“C”, so as to reproduce or form the panoramic image PF (one-row matriximage) with a picture angle of 180° shown in FIG. 5.

An advantage of the panoramic imaging device 1 according to the presentembodiment is that the respective unit images F1-1, F1-3, . . . havesubstantially no distortions at peripheries thereof because the centerlens L2-2 and the side lenses L1-1, L1-3, L3-1, L3-3 have a captureangle as small as 36° (which is smaller than approximately 60°), so thatno complex process of distortion correction for the respective unitimages is required when combining the unit images. Furthermore, sinceeach of the unit images F1-1, F1-3, is an image in a range ofapproximately 36°, the five unit images can be combined withsubstantially no overlap between adjacent two of the unit images. Thus,the panoramic imaging device 1 can combine multiple images into apanoramic image without complex image correction and without causingunnatural transition between adjacent images to remain, and furtherwhich can be reduced in volume and thickness in its entirety.

Note that the image reproduction microprocessor 6 in the presentembodiment performs image processing based on the image information ofthe unit image F2-2 of “C” at the center of the photodetector array 3.However, as shown e.g. in the left matrix image of FIG. 5, each of theunit images F1-2, F2-1, F2-3, F3-2 is also an image of “C” correspondingto the image segment of “C” at the center of the target object B.Accordingly, it is also possible for the image reproductionmicroprocessor 6 to reproduce a panoramic image PF by using the imageinformation of one of the unit images F1-2, F2-1, F2-3, F3-2. In thiscase, one of the optical lenses L1-2, L2-1, L2-3, L3-2 used for formingthe one of the unit images F1-2, F2-1, F2-3, F3-2, which is used for thereproduction of the panoramic image PF here, corresponds to and servesas the “center lens” defined above and in claims 1 and 5. Conversely, ifthe unit images F1-2, F2-1, F2-3, F3-2 are not used to reproduce apanoramic image PF, the optical lenses L1-2, L2-1, L2-3, L3-2 can beomitted. Alternatively, stop apertures corresponding to the respectiveoptical lenses L1-2, L2-1, L2-3, L3-2 can be closed so as to preventunit images from being formed at row 1-column 2 position, row 2-column 1position, row 2-column 3 position and row 3-column 2 position.

Referring now to FIG. 6 and FIG. 7, panoramic imaging devices 1according to a first modified example and a second modified example ofthe present embodiment will be described hereinafter. As shown in FIG.6, the panoramic imaging device 1 according to the first modifiedexample has six 45-45-90 right-angle prisms P1-1, P1-3, P2-1, P2-3,P3-1, P3-3 placed facing optical lenses L1-1, L1-3, L2-1, L2-3, L3-1,L3-3, respectively. The 45-45-90 right-angle prisms P1-1, P1-3 in thefirst row, those P3-1, P3-3 in the third row, and those P2-1, P2-3 inthe second row are inclined to the optical lens array 9 at the largestangle, the smallest angle and an intermediate angle, respectively.

Because of the largest inclination relative to the optical lens array 9,the 45-45-90 right-angle prisms P1-1, P1-3 in the first row bend andcollect lights entering in the left and right ranges closest to thefront range in the capture angle. Because of the smallest inclinationrelative to the optical lens array 9, the 45-45-90 right-angle prismsP3-1, P3-3 in the third row bend and collect lights entering in the leftand right ranges farthest from the front range in the capture angle. Onthe other hand, because of the intermediate inclination relative to theoptical lens array 9, the 45-45-90 right-angle prisms P2-1, P2-3 in thesecond row bend and collect lights entering in the intermediate left andright ranges from the front range in the capture angle.

More specifically, the optical lens L2-2 at the center receives lightentering in a front range of approximately 26° among lights entering inthe capture angle of 180°. This optical lens L2-2 corresponds to andserves as the “center lens”. The capture angle of 180° less the frontrange of approximately 26 is divided into left and right ranges each ofapproximately 77°, which are further divided into three pairs of leftand right ranges that are a pair closest to the front range, anintermediate pair and a pair farthest from the front range. In eachpair, each of the left and right ranges is a range of approximately 26°.The 45-45-90 right-angle prisms P1-1, P1-3 respectively bend and collectlights entering in the pair of left and right ranges, each ofapproximately 26°, which are closest to the front range, so as to allowthe lights to enter the optical lenses L1-1, L1-3.

Further, the 45-45-90 right-angle prisms P2-1, P2-3 respectively bendand collect lights entering in the pair of left and right ranges, eachof approximately 26°, which are intermediate or next closest to thefront range, so as to allow the lights to enter the optical lenses L2-1,L2-3. On the other hand, the 45-45-90 right-angle prisms P3-1, P3-3respectively bend and collect lights entering in the pair of left andright ranges, each of approximately 26°, which are farthest the frontrange, so as to allow the lights to enter the optical lenses L3-1, L3-3.According to the first modified example, the six optical lenses L1-1,L1-3, L2-1, L2-3, L3-1, L3-3 correspond to and serve as the “sidelenses”.

As a result, the panoramic imaging device 1 of the first modifiedexample forms, on the photodetector array 3, seven unit images composedof a unit image corresponding to the front range of approximately 26°and six unit images corresponding to the three pairs of left and rightranges each of approximately 26° as divided from the left and rightranges each of approximately 77°. The panoramic imaging device 1combines the seven unit images to reproduce a panoramic image PF. Sinceeach of the optical lenses L1-1, L1-2, . . . is only required to have acapture angle as small as 26°, the panoramic imaging device 1 of thefirst modified example enables a further reduction of the distortion ineach unit image formed on the photodetector array 3 as well as a furtherreduction of the unnatural transition between adjacent images combinedand reproduced into a panoramic image PF. Note that instead of dividingeach of the left or right ranges each of approximately 77° (less thefront range of approximately 26°) into three ranges each ofapproximately 26°, it is possible to divide each of the left and rightranges each of approximately 77° into another set of three ranges suchas 30°, 25° and 22° As shown in FIG. 7, the panoramic imaging device 1according to the second modified example has an optical lens array 9 of1 (one) row and 5 (five) columns, in which four 45-45-90 right-angleprisms P1-1, P1-2, P1-4, P1-5 are placed facing the optical lenses L1-1,L1-2, L1-4, L1-5, respectively. Correspondingly, the photodetector array3 is formed to have an elongated shape so as to form the one row-fivecolumn unit images thereon. According to the second modified example,the four optical lenses L1-1, L1-2, L1-4, L1-5 correspond to and serveas the “side lenses”, while the center optical lens L1-3 corresponds toand serves as the “center lens”. The 45-45-90 right-angle prisms P1-2,P1-4 are fixed and inclined to the optical lens array 9 at a relativelylarge angle, while those P1-1, P1-5 are fixed and inclined to theoptical lens array 3 at a relatively small angle. Thus, the 45-45-90right-angle prisms P1-2, P1-4 bend and collect lights entering in theleft and right ranges (first left and right ranges) closer to the frontrange in the capture angle corresponding to the optical lens L2-2. Onthe other hand, the 45-45-90 right-angle prisms P1-1, P1-5 bend andcollect lights entering in the left and right ranges (second left andright ranges) farther from the front range in the capture angle.

As a result, the panoramic imaging device 1 of the second modifiedexample forms, on the photodetector array 3, five unit images composedof a unit image corresponding to the front range and four unit images inthe first left and right ranges and the second left and right ranges.The panoramic imaging device 1 combines the five unit images toreproduce a panoramic image PF. Since each of the optical lens array 9and the photodetector array 3 is significantly reduced in area, thepanoramic imaging device 1 can be further reduced in volume andthickness. Note that in the present embodiment including the first andsecond modified examples, the prisms to bend and collect the lightsentering in left and right ranges in a capture angle to guide the lightsto the side lenses are not limited to 45-45-90 right-angle prisms, butcan be 30-60-90 right-angle prisms or equilateral triangular prisms.

Also note that the above-described embodiment describes the case wherethe picture angle of the panoramic image is approximately 180°. However,it is apparent that the picture angle of the panoramic image can beexpanded by simply increasing the capture angle or range of each prismused to bend, collect and guide light to each optical lens. Further notethat the above-described embodiment describes the case where the capturerange of each prism and optical lens is approximately 36° orapproximately 26° or the like. However, the capture range is not limitedto such ones and can be any one less than approximately 60°. It isapparent that the advantage of the panoramic imaging device 1 can beenjoyed if the capture range for each prism and optical lens is smallerthan approximately 60°, because thereby an optical lens which does notcause image distortion can be used for each of the capture ranges.

As described in the foregoing, in the panoramic imaging device 1according to the present embodiment, the capture angle less the frontrange is divided into left and right ranges, which are further dividedinto multiple pairs of left and right ranges, such that lights enteringin the multiple pairs of left and right ranges are bent and collected byprisms respectively positioned corresponding to the multiple pairs ofranges so as to be guided to the respective side lenses. Accordingly,the panoramic imaging device 1 can be formed without using opticallenses having a large capture angle (wide-angle lenses) such as 60° orlarger, making it possible for the formed unit images to havesubstantially no distortions, so that no complex process of imagecorrection for the unit images is required when combining the unitimages, and that the unit images can be combined into a panoramic imagePF of a picture angle of at least or approximately 180° without causingunnatural transition between adjacent unit images. This also makes itpossible to reduce the volume and thickness of the entire panoramicimaging device 1.

The present invention has been described above using presently preferredembodiments, but such description should not be interpreted as limitingthe present invention. Various modifications will become obvious,evident or apparent to those ordinarily skilled in the art, who haveread the description. Accordingly, the appended claims should beinterpreted to cover all modifications and alterations which fall withinthe spirit and scope of the present invention.

This application is based on Japanese patent application 2006-219158filed Aug. 11, 2006, the content of which is hereby incorporated byreference.

1. A panoramic imaging device comprising: an optical lens system forcollecting light entering in a capture angle of at least 180° so as toform images on a predetermined focal plane; imaging means placed at thefocal plane for converting the images formed by the optical lens systemto electronic image information; and image reproducing means forsubjecting the electronic image information obtained from the imagingmeans to imaging processing so as to reproduce a panoramic image,wherein the optical lens system comprises: an optical lens arrayincluding a center lens having an optical axis and formed on one planefor receiving light entering in a front range in the capture angle, andalso including pairs of left and right side lenses formed on the oneplane and on left and right sides of the center lens, respectively, andwhich have optical axes parallel to that of the center lens, so as torespectively receive lights entering in left and right ranges in thecapture angle, which are divided into pairs of left and right rangessuch that the pairs of left and right side lenses receive lightsentering in the divided pairs of the left and right ranges,respectively; and prisms placed on a light entrance side of the sidelenses for bending and collecting the lights entering in the dividedpairs of the left and right ranges in the capture angle for the sidelenses to receive, so as to guide and direct the lights to, and alongthe optical axes of, the side lenses, respectively; wherein the imagingmeans is formed of a photodetector array placed at a predetermineddistance from, and in parallel to, the optical lens array for capturingan image formed by the center lens and images formed by the left andright side lenses; and wherein the image reproducing means combines theimage formed by the center lens in the front range in the capture anglewith the images respectively formed by the pairs of left and right sidelenses in the divided pairs of left and right ranges in the captureangle so as to reproduce a panoramic image with a picture angle of atleast 180°; and wherein each of the lights received by the center lensand the side lenses is light entering in a range smaller thanapproximately 60° in the capture angle of at least 180°.
 2. Thepanoramic imaging device according to claim 1, wherein the capture angleis approximately 180°, wherein the light received by the center lens islight entering in a front range of approximately 36° in the captureangle, and wherein the side lenses are composed of two left side lensesand two right side lenses which receive lights entering in divided twopairs of left and right ranges each of approximately 36°, respectively,which enter in a pair of left and right ranges each of approximately 72°in the capture angle, respectively.
 3. The panoramic imaging deviceaccording to claim 1, wherein the capture angle is approximately 180°,wherein the light received by the center lens is light entering in afront range of approximately 26° in the capture angle, and wherein theside lenses are composed of three left side lenses and three right sidelenses which receive lights entering in divided three pairs of left andright ranges each of approximately 26°, respectively, which enter in apair of left and right ranges each of approximately 77° in the captureangle, respectively.
 4. A panoramic imaging device comprising: anoptical lens system for collecting light entering in a capture angle ofapproximately 180° so as to form images on a predetermined focal plane;imaging means placed at the focal plane for converting the images formedby the optical lens system to electronic image information; and imagereproducing means for subjecting the electronic image informationobtained from the imaging means to imaging processing so as to reproducea panoramic image, wherein the optical lens system comprises: an opticallens array including a center lens having an optical axis and formed onone plane for receiving light entering in a front range of approximately36° in the capture angle, and also including two pairs of left and rightside lenses formed on the one plane and on left and right sides of thecenter lens, respectively, and which have optical axes parallel to thatof the center lens, so as to respectively receive lights entering inleft and right ranges each of approximately 72° in the capture angle,which are divided into two pairs of left and right ranges each ofapproximately 36° such that the two pairs of left and right side lensesreceive lights entering in the divided two pairs of the left and rightranges, respectively; and two pairs of left and right right-angle prismsplaced on a light entrance side of the side lenses, and respectivelyfacing the side lenses at positions to prevent interruption of the lightentering the center lens in the front range of approximately 36°, forbending and collecting the lights entering in the divided two pairs ofthe left and right ranges each of approximately 36° in the capture anglefor the side lenses to receive, so as to guide and direct the lights to,and along the optical axes of, the side lenses, respectively, whereinthe imaging means is formed of a photodetector array placed at apredetermined distance from, and in parallel to, the optical lens arrayfor capturing an image formed by the center lens and images formed bythe two pairs of left and right side lenses, and wherein the imagereproducing means combines the image formed by the center lens in thefront range of approximately 36° in the capture angle with four imagesrespectively formed by the two pairs of left and right side lenses inthe divided two pairs of left and right ranges each of approximately 36°in the capture angle so as to reproduce a panoramic image with a pictureangle of approximately 180°.